Intrinsically safe data network

ABSTRACT

An intrinsically safe data network, such as one defining a system for acquiring and transferring data from inside a hazardous zone at an oil or gas well to outside the hazardous zone, includes a fixed number of at least one data signal conductor and a fixed number of at least one intrinsic safety barrier forming part of the overall network that allows for the use of more transducers than there are intrinsic safety barrier(s).

BACKGROUND OF THE INVENTION

This invention is an intrinsically safe data network, such as a systemfor acquiring and transferring data from inside a hazardous zone at anoil or gas well to outside the hazardous zone.

It is well known that oil and gas well locations can have hazardouszones such as due to the presence of flammable liquids and gases. Thesesubstances can be electrically ignited.

Although these zones and dangers are known to exist at oil and gas wellsites, electrical equipment sometimes must be used in these areas to,for example, sense data such as temperature, pressure and flow rate.When this equipment is used, precautions must be taken to avoidaccidents from occurring in these zones. These precautions include usingwithin these zones electrical equipment that meets known standards whichqualify the equipment as "intrinsically safe." For example, certifiedintrinsically safe transducers and intrinsic safety barriers (devicesthat connect the transducers to equipment outside the hazardous zone)are used to obtain data and permit its communication to a computerlocated at the well site but outside the hazardous zone.

Prior systems of such transducers and intrinsic safety barriers haveprovided a safe means for obtaining data from inside a hazardous zoneand communicating that data outside the hazardous zone; however, suchsystems have a shortcoming, namely, each conductor or conductor pairfrom every transducer must have a respective intrinsic safety barrierfor that conductor or conductor pair to be connected outside thehazardous zone. This can be expensive if several transducers need to beused. Furthermore, a supply of intrinsic safety barriers must be kept onhand in the event additional transducers are needed in the hazardouszone. Another shortcoming of this type of system, wherein eachtransducer directly communicates to a device outside the hazardous zone,is that the external device must have enough inputs to receive thesignals from each of the transducers.

In view of these shortcomings there is the specific need for anintrinsically safe data network wherein the number of intrinsic safetybarriers needed is limited to a predetermined number without effectivelylimiting the number of transducers that can be used ("withouteffectively limiting" being interpreted in view of some maximum numberof transducers that would ever actually be used in any particularinstallation, such as at a typical oil and gas well location).

SUMMARY OF THE INVENTION

The present invention overcomes the above-noted and other shortcomingsof the prior art by providing a novel and improved intrinsically safedata network. More specifically, the present invention provides a systemfor acquiring and transferring data from inside a hazardous zone at anoil or gas well to outside the hazardous zone. This invention includes afixed, predetermined number of one or more intrinsic safety barriers,but it allows for the use of more transducers than there are intrinsicsafety barriers. This provides for reduced cost since an intrinsicsafety barrier is not needed for each transducer. This also enhancesflexibility and facilitates installation since the number of transducersused in a hazardous zone can be changed without having to install orremove corresponding intrinsic safety barriers.

The intrinsically safe data network for communicating from inside ahazardous zone to outside the hazardous zone comprises a plurality oftransducers for use within the hazardous zone. Each transducer has atleast one electrical conductor for conducting an analog electricalsignal representing a parameter sensed by the respective transducer. Thenetwork further comprises transducer communication interface means forconnecting to the plurality of transducers within the hazardous zone andfor converting the analog electrical signals from the plurality oftransducers into respective data signals. The network still furthercomprises boundary crossing connector means for conducting the datasignals from the transducer communication interface means within thehazardous zone to a location outside the hazardous zone. This boundarycrossing connector means includes a predetermined plurality of signalconductors, wherein the predetermined plurality is less than the numberof electrical conductors of the plurality of transducers. The boundarycrossing connector means also includes a predetermined number of atleast one intrinsic safety barrier connected to the signal conductors.Preferably the number of one or more intrinsic safety barriers is notgreater than the number of signal conductors.

Stated another way, the present invention provides a system foracquiring and transferring data from inside a hazardous zone at an oilor gas well to outside the hazardous zone, comprising: a communicationconnection network including a fixed number of at least one data signalconductor and a fixed number of at least one intrinsic safety barrier,each intrinsic safety barrier connected within at least a respectivedata signal conductor so that one end of the respective conductor isdisposed within the hazardous zone and the other end of the respectiveconductor is disposed outside the hazardous zone; a plurality oftransducers disposed in the hazardous zone; and means for receivingsignals from the transducers, processing received signals into datasignals, and communicating the data signals over the fixed number of atleast one data signal conductor so that only the fixed number of atleast one data signal conductor and the fixed number of at least oneintrinsic safety barrier are needed for communicating data signals outof the hazardous zone regardless of the number of the plurality oftransducers used at an actual oil or gas well.

Therefore, from the foregoing, it is a general object of the presentinvention to provide a novel and improved intrinsically safe datanetwork and, more particularly, a system for acquiring and transferringdata from inside a hazardous zone at an oil or gas well to outside thehazardous zone. Other and further objects, features and advantages ofthe present invention will be readily apparent to those skilled in theart when the following description of the preferred embodiments is readin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram depicting one embodiment of the presentinvention.

FIG. 2 is a block diagram of another embodiment of the presentinvention.

FIG. 3 is a block diagram representing a particular implementation ofthe present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An intrinsically safe data network in accordance with the presentinvention is illustrated in FIG. 1. The network includes a plurality oftransducers 2, transducer communication interface means 4, boundarycrossing connector means 6, and external processing means 8. Thetransducers 2 and the transducer communication interface means 4, alongwith part of the boundary crossing connector means 6, are disposed in ahazardous zone, such as in a gaseous environment at an oil or gas well.The other portion of the boundary crossing connector means 6 and theexternal processing means 8 are located outside the hazardous zone asindicated in FIG. 1.

The transducers 2 are of a type suitable for use within the hazardouszone. Preferably these are certified intrinsically safe, which is a typeof transducer known in the art. Transducers in general are devices thatconvert physical properties, such as heat, pressure, differentialpressure, flow rate, etc., into measurable electrical signals.Typically, such quantities as temperature, pressure, etc., are convertedto analog electrical voltage or current outputs. Flow rates aretypically output as a frequency of an electrical signal. To provide itsrespective analog electrical signal representing a measurement of therespective physical parameter or property, each transducer has at leastone electrical conductor for conducting the signal.

In prior systems, the electrical conductors from the transducers 2connect to respective intrinsic safety barriers in passing outside thehazardous zone to some type of processing equipment. In the presentinvention, however, each of the electrical conductors from thetransducers 2 is connected to the transducer communication interfacemeans 4. This is represented in FIG. 1 by the "N" number of conductorsextending between the transducers 2 and the transducer communicationinterface means 4. These connections can be implemented by connecting asingle transducer to a respective interface forming the means 4, ormultiple transducer conductors can be connected to a common or sharedinterface of the means 4.

The transducer communication interface means 4 can be a circuit simplyproviding a networking capability whereby signals from the transducers 2are communicated over a common predetermined number of conductors of theboundary crossing connector means 6. Preferably, however, the transducercommunication interface means 4 provides at least the capability ofconverting the typically analog transducer output signals to a digitalformat. This can be accomplished by a conventional analog-to-digitalconverter combined with a networking capability. Even more preferably,the transducer communication interface means 4 can also include aprocessing capability, such as one which provides correction factors indetermining actual measured parameter values. This would, for example,convert a 0-5 volt dc signal representing 0-100 psig pressure into adigital format specifying the actual corrected pressure measurement.Converting the analog transducer output signals to digital signalsreduces or eliminates any noise effects that can be present in thehazardous zone where the present invention is to be used.

Thus, from the foregoing, the transducer communication interface means 4connects to the plurality of transducers 2 within the hazardous zone andpreferably converts the analog electrical signals into respective datasignals. More specifically, the preferred means 4 receives signals fromthe transducers, processes the received signals into data signals, andcommunicates the data signals over the boundary crossing connector means6. Because the boundary crossing connector means 6 has a fixed number ofdata signal conductors as explained below, the transducer communicationinterface means 4 enables the data signals it provides to becommunicated over this fixed number of data signal conductors. Only thisfixed number of data signal conductors, and a fixed number of intrinsicsafety barriers forming another part of the boundary crossing connectormeans 6 as further explained below, are needed for communicating datasignals out of the hazardous zone regardless of the number oftransducers used at an actual hazardous zone such as one at an actualoil or gas well. It will be apparent that the foregoing can beimplemented by what could be referred to as "smart" transducers, namelytransducers with some type of processing and/or networking capability.This can be individual transducers having their own "intelligence"components or multiple transducers connected to a common "intelligent"device as referred to above.

A system having multiple individual "smart" transducers or the like orhaving multiple common configurations is illustrated in FIG. 2. Each"internal site" 10 identified in FIG. 2 represents either an individualtransducer with its respective intelligent circuit or a site wheremultiple transducers communicate with a common interface. These multipleinternal sites 10 within the hazardous zone are each connected to acommunication connection network defining a particular embodiment of theboundary crossing connector means 6.

The boundary crossing connector means 6 conducts the data signals fromthe transducer communication interface means 4 within the hazardous zoneto a location outside the hazardous zone. The boundary crossingconnector means 6 includes one or more, and preferably a predeterminedplurality of signal conductors 12. The boundary crossing connector means6 also includes a predetermined number of one or more intrinsic safetybarriers 14 preferably of a number not greater than the number of signalconductors 12. Each intrinsic safety barrier 14 is connected to at leastone of the signal conductors 12 of the boundary crossing connector means6. The numbers of conductors 12 and intrinsic safety barriers 14 areless than the number "N" of electrical conductors of the plurality oftransducers 2 so that not as many intrinsic safety barriers 14 areneeded as would be needed if the transducers connected directly acrossthe boundary of the hazardous zone.

The signal conductors 12 can be any suitable type, but in the preferredembodiment they are electrical signal conductors such as ones made ofmetal wire. As shown in FIGS. 1 and 2, one end of the conductors 12 islocated in the hazardous zone, being connected to the transducerinterface means 4 of one or more internal sites 10; and the other end ofthe conductors 12 is connected outside the hazardous zone, such as tothe external processing means 8.

Connected intermediate the two ends of each conductor is an intrinsicsafety barrier 14. This is a known type of device, one example of whichis the MTL700 series (specifically, for example, Model MTL765) from MTLInstruments Group PLC.

When multiple sites 10 are connected to the conductors 12, the boundarycrossing connector means 6 defines the communication connection networksuch as illustrated in FIG. 2 where the multiple internal sites 10a-10xare connected to the conductors 12. FIG. 2 also shows that externalsites 16a-16y can be connected to the conductors 12 between theintrinsic safety barrier(s) 14 and the external processing means 8. Allof these internal and external sites can be connected without addingadditional conductors 12 or additional intrinsic safety barriers 14because the numbers of conductors 12 and intrinsic safety barriers 14are fixed regardless of the number of transducers 2 used.

FIGS. 1 and 2 illustrate that the conductors 12 connect to an externalprocessing means 8. This is equipped with networking capabilities whichonly need to connect to the predetermined number of conductors 12without needing to have individual inputs to receive the voltage,current or frequency outputs provided by the respective transducers 2.

The external processing means 8 can be implemented by any suitabledevice or devices. One type is a programmable logic controller. Anotherexample is a programmed computer. In the preferred embodiment, these areprogrammed to organize the information derived from the digital datasignals representing the measured physical parameters into a coherentreport. The specific nature of the external processing means 8 is notmaterial to the present invention. The significance instead is merelythat the external processing means 8 connects to the conductors 12 (andthus to the intrinsic safety barrier(s) 14) outside the hazardous zone,and the external processing means 8 receives the data signals conductedover the signal conductors 12 through the intrinsic safety barriers 14for further processing not inventively material to the presentinvention.

Referring to FIG. 3, a specific implementation of the present inventionwill be described. This is specifically a system for acquiring andtransferring data from inside a hazardous zone at an oil or gas well tooutside the hazardous zone.

Located within the hazardous zone of the FIG. 3 implementation are atemperature transducer 2a, a pressure transducer 2b and a flowtransducer 2c, each certified intrinsically safe. Each of these providesa respective analog electrical signal output to a gas flow computer 18implementing the transducer communication interface means 4. The detailsof the gas flow computer 18 are not important to the present inventionas it can be implemented in any suitable manner; however, it preferablyis able to read the analog signals from the transducers 2a, 2b, 2c andconvert them into corrected digital values defining the measuredconditions. A specific example of such a gas flow computer is one fromHalliburton Energy Services in Duncan, Okla. Forming part of the gasflow computer 18 is an RS-485 interface 20 which is any suitable circuitconforming to the RS-485 standard known in the art (a specific circuitis one provided by Halliburton Energy Services). The RS-485 standardprovides for two communication lines identified in FIG. 3 as conductors12a, 12b. Thus, the data conductors 12a, 12b are of fewer number thanthe transducers 2a, 2b, 2c and their output electrical conductors.Furthermore, only two conductors 12a, 12b are needed regardless of thenumber of additional transducers that can be added (up to a total numberof thirty-two sites 10, 16 can be connected to the two conductors 12a,12b as defined by the RS-485 standard, and there can be multipletransducers at each site).

The conductor 12a connects to another RS-485 interface 20 in theexternal processing means 8 through a respective intrinsic safetybarrier 14a, and the conductor 12b connects to the interface 20 of theexternal processing means 8 through a respective intrinsic safetybarrier 14b. Although separate intrinsic safety barriers 14a, 14b areshown in FIG. 3, a single barrier unit such as the model MTL765 ac unitcan be used since it provides barrier protection for two wires;therefore, there can be fewer intrinsic safety barriers 14 thanconductors 12.

The two data signal conductors 12a, 12b define a network bus. The "othersites" indicated in FIG. 3 connect in electrical parallel to this bus.One way to do this is to use a four-conductor shielded RS-485 cableconnected to each site. The shields are commonly grounded (with thepower system ground). One pair of the four wires of one such cabledefines conductors 12a, 12b. One wire of the other pair of this cableconnects at one end to the conductor 12a and connects at its other endto one wire of the cable for another site; the other wire of the otherpair of wires of the cable at the first site connects at one end to theconductor 12b and connects at its other end to a second wire of thecable for the other site. The other two wires at the other site connectin this same manner between the second and third site, and so on. At thelast site, the second pair of wires of the respective cable connects toa line termination circuit for the pertinent communication standard. ForRS-485, this can be a series resistor-capacitor circuit (120 ohm-0.001microfarad) connected between the two wires of the second pair. The sametype termination circuit is also connected at the end of the conductors12a, 12b connected to the intrinsic safety barrier(s) 14.

Although the FIG. 3 implementation uses the RS-485 standard and anetwork bus configuration in accordance with that standard, other typesof standards and network configurations can be used. For example, a ringstructure or a double bus structure can be used. Examples of other datanetwork standards are IEEE 802.3, IEEE 802.5 and IEEE 802.6.

The RS-485 standard allows up to thirty-two transducer communicationinterface means 4 to be connected to the single RS-485 bus. Asexplained, a single RS-485 bus consists of two wires for signal, and apossible third conductor (e.g., the cable shield) to assure electricalgrounds are at the same potential. Maximum combined cable length isapproximately 4,000 feet, with a maximum transmission speed of 10megabytes per second. The inclusion of additional sites to this networkis simple as the respective transducer communication interface means 4of each additional site merely taps into the two or three wire bus asillustrated in FIG. 3 and explained above. Specifically for the FIG. 3implementation, additional interfaces 20 would be connected inelectrical parallel to the conductors 12a, 12b.

Although not illustrated in the drawings, another conductor that may beused and that intersects the hazardous zone boundary is one or morepower conductors to provide external power to the internal sites withinthe hazardous zone. This can be accomplished in a conventional mannerknown in the art and is outside the scope of the present invention whichis directed to the data transmission network.

Thus, the present invention is well adapted to carry out the objects andattain the ends and advantages mentioned above as well as those inherenttherein. While preferred embodiments of the invention have beendescribed for the purpose of this disclosure, changes in theconstruction and arrangement of parts and the performance of steps canbe made by those skilled in the art, which changes are encompassedwithin the spirit of this invention as defined by the appended claims.

What is claimed is:
 1. A system for acquiring and transferring data frominside a hazardous zone at an oil or gas well to outside the hazardouszone, comprising:a communication connection network including a fixednumber of at least one data signal conductor and a fixed number of atleast one intrinsic safety barrier, each said intrinsic safety barrierconnected within at least a respective data signal conductor so that oneend of the respective conductor is disposed within a hazardous zone atan oil or gas well and the other end of the respective conductor isdisposed outside the hazardous zone, wherein said communicationconnection network includes two data signal conductors; a plurality oftransducers disposed in the hazardous zone; and means for receivingsignals from said transducers, processing received signals into datasignals, and communicating said data signals over said fixed number ofat least one data signal conductor so that only said fixed number of atleast one data signal conductor and said fixed number of at least oneintrinsic safety barrier are needed for communicating data signals outof the hazardous zone regardless of the number of said plurality oftransducers used at an actual oil or gas well, wherein said means forreceiving, processing and communicating includes a plurality of RS-485interface means connected in electrical parallel to said two data signalconductors for effecting communications over said two data signalconductors in RS-485 format.
 2. A system as defined in claim 1,wherein:said means for receiving, processing and communicating includesa gas flow computer having said RS-485 interface means therein; and saidplurality of transducers includes a temperature transducer, a pressuretransducer and a flow transducer connected to said gas flow computerwithin the hazardous zone.
 3. A system as defined in claim 2, furthercomprising external processing means for connecting to saidcommunication connection network outside the hazardous zone and forreceiving the data signals conducted over said data signal conductorsthrough said at least one intrinsic safety barrier.
 4. A system asdefined in claim 3, wherein there is a single intrinsic safety barrierunit connected to both of said two data signal conductors.
 5. Anintrinsically safe data network for communicating from inside ahazardous zone to outside the hazardous zone, comprising:a plurality oftransducers for use within the hazardous zone, each transducer having atleast one electrical conductor for conducting an electrical signalrepresenting a parameter sensed by the respective transducer; boundarycrossing connector means for conducting data signals from within thehazardous zone to a location outside the hazardous zone, said boundarycrossing connector means including:a fixed predetermined plurality ofsignal conductors, wherein said fixed predetermined plurality is lessthan the number of said electrical conductors of said plurality oftransducers; and a fixed predetermined number of at least one intrinsicsafety barrier connected to said signal conductors; and a plurality oftransducer communication interface means for use at a plurality ofinternal sites within the hazardous zone, each said interface meansconnected to a respective group of at least one of said plurality oftransducers inside the hazardous zone and each said interface meansconnected in electrical parallel to the same said fixed predeterminedplurality of signal conductors inside the hazardous zone, forcommunicating onto said signal conductors data signals responsive to theelectrical signals of said plurality of transducers.
 6. A network asdefined in claim 5, further comprising external processing means forconnecting to said boundary crossing connector means outside thehazardous zone and for receiving the data signals conducted over saidsignal conductors through said at least one intrinsic safety barrier. 7.A network as defined in claim 6, wherein there are two said signalconductors and there is a single intrinsic safety barrier connected toboth of said two signal conductors.
 8. A network as defined in claim 7,wherein:at least one of said transducer communication interface meansincludes a gas flow computer; and said plurality of transducers includesa temperature transducer, a pressure transducer and a flow transducerconnected to said gas flow computer within the hazardous zone.